Biodiversity Net Gain (BNG) is a framework designed to ensure that developments leave the natural environment in a better state than before. With the UK’s biodiversity under increasing pressure, BNG offers a way to balance economic growth with ecological restoration. It ensures that development projects result in an overall improvement in biodiversity, contributing to the UK’s broader environmental goals.
What is Biodiversity Net Gain?
In the UK, BNG requires developers to leave the natural environment in a better condition than it was before their projects began. Mandated by the Environment Act 2021, most new developments in England must deliver at least a 10% net gain in biodiversity, calculated using the Defra Biodiversity Metric. This metric assesses the ecological value of existing habitats based on their type, quality, distinctiveness and condition.
For example, if a development leads to the loss of 1 hectare of low-quality grassland, the developer might compensate by creating 1.2 hectares of higher-quality wildflower meadows nearby or by enhancing an existing habitat. The goal is to ensure that any ecological losses from a development are outweighed by biodiversity gains so that the development ultimately delivers tangible wildlife and ecosystem benefits.
Why is BNG Important in the UK?
Many people argue that the UK is currently facing a biodiversity crisis, with significant habitat loss and species declines over recent decades. Reports such as the State of Nature 2019 highlight that 41% of UK species have declined since 1970. Drivers of this decline include urbanisation, agricultural intensification and climate change.
BNG represents a proactive response to this crisis by embedding nature recovery into property development. It aligns with the government’s 25-Year Environment Plan, which aims to reverse biodiversity loss, improve natural capital and leave the environment in better shape for future generations.
How Does Biodiversity Net Gain Work in Practice?
Baseline Habitat Assessment: Developers must first arrange a Biodiversity Net Gain survey to establish its current biodiversity value, using the Defra Biodiversity Metric.
Design for Avoidance and Minimisation: The project is designed to avoid harming high-value habitats (e.g. irreplaceable habitat, such as ancient woodlands) and minimise impacts on other features.
Compensation Through Habitat Creation: Where harm cannot be avoided, developers must deliver compensatory measures. These could include creating new habitats, such as grasslands, woodlands or wetlands, or improving the condition of nearby habitats.
Long-Term Monitoring and Management: Biodiversity gains must be secured and effectively managed for at least 30 years. Compliance being overseen by the local planning authority, supported by appropriate conservation bodies.
Challenges and Opportunities
While BNG has significant potential, it is not without its challenges. Crtics argue that the BNG metric can oversimplify complex ecosystems and place qual value on species and habitats that are more common and in less need of saving. Thus opportunities could be missed to fully appreciate the ecological value of some sites, which could result in their loss.
Another major concern is the reliance on off-site compensation. While BNG ideally encourages developers to enhance biodiversity within their project boundaries, in practice, many developments will offset their impact by funding habitat creation elsewhere. Ecologists fear that this could lead to the loss of valuable local ecosystems, particularly in urban areas, in exchange for biodiversity gains in remote locations that do not benefit the affected communities.
Initiatives such as the Nature Recovery Network aim to create a strategic approach to BNG, ensuring habitat enhancements contribute to wider ecological connectivity and national biodiversity goals.
A Biodiverse Future
Despite the challenges surrounding BNG, there is general agreement that the principle of developments enhancing biodiversity is a good one.
It is still early days for BNG, and it is hoped that revisions and updates to the assessment and implementation processes will vastly improve its effectiveness.
In the meantime, there is much that consultants like Phlorum can do to help guide all sides through the BNG process, so that it delivers what is needed now. It is in everyone’s interest that truly sustainable development that benefits biodiversity continues to shape our shared future.
Dr Paul Beckett is one of the UK’s leading experts in Japanese knotweed and is a member of the Expert Witness Institute. He regularly provides Japanese knotweed expert witness services. He helped produce the RICS knotweed guidance for surveyors and was integral in the formation of the Property Care Association (PCA) Invasive Weed Control Group (IWCG).
